From: Gao Feng <f...@ikuai8.com>

Current SYNPROXY codes return NF_DROP during normal TCP handshaking,
it is not friendly to caller. Because the nf_hook_slow would treat
the NF_DROP as an error, and return -EPERM.
As a result, it may cause the top caller think it meets one error.

So use NF_STOLEN instead of NF_DROP now because there is no error
happened indeed, and free the skb directly.

Signed-off-by: Gao Feng <f...@ikuai8.com>
---
 net/ipv4/netfilter/ipt_SYNPROXY.c  | 7 ++++---
 net/ipv6/netfilter/ip6t_SYNPROXY.c | 6 ++++--
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/netfilter/ipt_SYNPROXY.c 
b/net/ipv4/netfilter/ipt_SYNPROXY.c
index 3240a26..9ed80d4 100644
--- a/net/ipv4/netfilter/ipt_SYNPROXY.c
+++ b/net/ipv4/netfilter/ipt_SYNPROXY.c
@@ -293,12 +293,13 @@
                                          XT_SYNPROXY_OPT_ECN);
 
                synproxy_send_client_synack(net, skb, th, &opts);
-               return NF_DROP;
-
+               consume_skb(skb);
+               return NF_STOLEN;
        } else if (th->ack && !(th->fin || th->rst || th->syn)) {
                /* ACK from client */
                synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq));
-               return NF_DROP;
+               consume_skb(skb);
+               return NF_STOLEN;
        }
 
        return XT_CONTINUE;
diff --git a/net/ipv6/netfilter/ip6t_SYNPROXY.c 
b/net/ipv6/netfilter/ip6t_SYNPROXY.c
index 4ef1ddd..d5d5725 100644
--- a/net/ipv6/netfilter/ip6t_SYNPROXY.c
+++ b/net/ipv6/netfilter/ip6t_SYNPROXY.c
@@ -307,12 +307,14 @@
                                          XT_SYNPROXY_OPT_ECN);
 
                synproxy_send_client_synack(net, skb, th, &opts);
-               return NF_DROP;
+               consume_skb(skb);
+               return NF_STOLEN;
 
        } else if (th->ack && !(th->fin || th->rst || th->syn)) {
                /* ACK from client */
                synproxy_recv_client_ack(net, skb, th, &opts, ntohl(th->seq));
-               return NF_DROP;
+               consume_skb(skb);
+               return NF_STOLEN;
        }
 
        return XT_CONTINUE;
-- 
1.9.1


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